Mobile devices such as phones and tablets are becoming the computing device of choice for users. Typically, these mobile devices store a variety of content items such as music, movies, and applications. Users are able to purchase and download content items directly to their mobile devices from online stores or marketplaces. As a result, mobile devices increasingly need a larger and larger amount of storage to accommodate the vast amounts of content items that are available.
As a solution to the increasing storage needs of mobile devices, some manufacturers of mobile device have included removable storage capabilities into their mobile devices. These removable storage capabilities include the ability to read and write from secure digital cards. However, for creators of content items, allowing users to store their content items on removable storage creates several drawbacks.
One such drawback is the ability to share the content items with other users. Because secure digital cards are removable from the mobile devices, and are readable by most personal computers, a user may download a content item such as an application, and may share the application with their friends by copying the contents of the secure digital card on their personal computer. In another example, a user may make some trivial changes to the source code of the application, and may attempt to sell or distribute the modified application as their own creation. Such sales or distribution may violate the intellectual property rights of the creators of the content items.
Another drawback of removable storage is application isolation. Typically, mobile devices execute applications in isolation from one another, using functionality provided by the file system used by the mobile device on the non-removable or internal storage of the mobile device. Secure digital cards often use file systems such as file allocation table (“FAT”) and extended file allocation table (“exFAT”) file systems which currently lack the isolation functionality of the file systems used by the mobile devices. As a result, a malicious user may use an application stored on the removable storage to interfere with the operation of another application, or content item, stored on the removable storage.